Sometimes, pressing the brake pedal is not enough to stop a vehicle, which is why technology like anti-lock brakes and brake override systems have become increasingly popular. Anti-lock brakes prevent the wheels from locking up when you slam on the brakes to help bring the vehicle safely to a stop. But what happens when the driver presses the gas and brake pedals at the same time? This is where the braking override system comes in.
The system has been around since the late 1980s, first used on the BMW 750 as a performance enhancer. BMW was able to easily integrate override brakes with the electric throttle system, as both are run electronically and tied to the car's computer. In 2001, the German automaker began including the technology on every one of their vehicles, and other car companies have since adopted the technology as well. In fact, last year Transportation Secretary Ray LaHood mentioned that the U.S. government was considering issuing a federal mandate that would require all new vehicles to include the technology.
When a driver presses both the acceleration and brake pedals at the same time, the system recognizes this action as unnatural and alerts the car's central computer, which has a number of methods to safely slow the vehicle down. Brake override can be engaged by adjusting the throttle position, altering the timing or reducing the amount of fuel reaching the combustion chamber. The chosen method depends on how the vehicle is programmed to respond, which varies from brand to brand.
Toyota's brake override systems, for example, take the vehicle's speed into consideration and does not activate for half a second in the vehicle is traveling 5 miles per hour or faster. This is so the override system does not kick in when it is not needed, such as when starting a vehicle on an incline or attempting to get traction in mud, snow or ice.
Brake override systems are programmed to react as a human would during accidental acceleration - by stopping the car. Since more vehicles are being built with electronic throttles that are capable of adjusting the vehicle speed, it makes sense that a system would be used to counteract the throttle in case it malfunctions.